<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>第四题</title>
</head>

<body>
    <script>
        let flag = true
        while (flag === true) {
            let username = prompt('请输入用户名')
            let password = prompt('请输入密码')
            if (username === 'admin' && password === '123456') {
                alert('登录成功')
                break
                flag = false
            } else {
                alert('用户名或者密码错误')
            }
        }
    </script>
</body>

</html>